KR101353350B1

KR101353350B1 - High-efficient Solar Cell using wide-band absorption and energy transfer

Info

Publication number: KR101353350B1
Application number: KR1020110116369A
Authority: KR
Inventors: 이주인; 한일기
Original assignee: 한국표준과학연구원
Priority date: 2011-11-09
Filing date: 2011-11-09
Publication date: 2014-01-21
Also published as: KR20130051174A

Abstract

The present invention provides a solar cell. The solar cell includes a first solar cell including an N-type semiconductor layer and a P-type semiconductor layer, and a heterojunction quantum dot having a core and a shell surrounding the core. Include. Heterojunction quantum dots absorb electrons and transfer electron-electron pairs formed to the first solar cell via Foster resonance energy transfer (FRET).

Description

High efficiency solar cell using broadband wavelength absorption and energy conversion

The present invention relates to a solar cell of the present invention, and more particularly, to a solar cell using a quantum dot having a quantum well structure.

In the photovoltaic power generation system, the share of solar cell module prices is large. On the other hand, costs other than solar cell modules, such as installation cost, land price required for installation, and maintenance cost, are in proportion to the total area of the solar cell. Therefore, increasing the efficiency of the solar cell can lower the production cost and the effect of lowering the manufacturing cost of the photovoltaic system. Therefore, a high efficiency solar cell is required.

One technical problem to be solved of the present invention is to provide a high efficiency solar cell using a quantum dot.

A solar cell according to an embodiment of the present invention includes a first solar cell including an N-type semiconductor layer and a P-type semiconductor layer; And a heterojunction quantum dot disposed on the first solar cell and having a core and a shell surrounding the core. The heterojunction quantum dot absorbs sunlight and transfers an electron-electron pair formed to the first solar cell through Poster resonance energy transfer (FRET).

In one embodiment of the present invention, the core comprises a group II-VI compound or group III-V compound, the cell is a barrier layer surrounding at least one pair of the core and the quantum well layer surrounding the Bayer layer The band gap of the barrier layer may be greater than the band gap of the core and quantum well layers, and the band gap of the quantum well layer may be greater than the band gap of the core.

In one embodiment of the present invention, the cell comprises: a first barrier layer surrounding the core; A first quantum well layer surrounding the first barrier layer; It may include a second barrier layer surrounding the first quantum well layer; and a second quantum well layer surrounding the second barrier layer. The band gap of the second quantum well layer may be larger than the band gap of the first quantum well layer.

In one embodiment of the present invention, the core may be PbS, the first barrier layer and the second barrier layer is ZnS, the first quantum well layer is CdSe, the second quantum well layer may be CdS. .

In one embodiment of the present invention, the first solar cell may be a group III-V compound, a group IV semiconductor, and an organic material.

In one embodiment of the present invention, the first solar cell further comprises an intrinsic semiconductor layer disposed between the N-type semiconductor layer and the P-type semiconductor layer, the intrinsic semiconductor layer is Si quantum dots, Ge quantum dots, InAs Quantum dots, or InGaAs quantum dots.

In one embodiment of the present invention, the N-type semiconductor layer or the P-type semiconductor layer is disposed in contact with the heterojunction quantum dots, the thickness of the N-type semiconductor layer or the P-type semiconductor is several nanometers (nm) Can be.

In one embodiment of the present invention, further comprising a protective film surrounding the quantum dot, the band gap of the first solar cell may be smaller than the band gap of the core.

Synthesis of a colloidal semiconductor quantum dot having a semiconductor heterojunction structure made of another material according to one embodiment of the present invention does not require complicated growth equipment or a difficult process. Therefore, the synthesis of the semiconductor quantum dots can be performed inexpensively. The quantum dot includes a heterojunction structure having a large difference in band gap. Thus, the quantum dot can easily absorb light of a wideband wavelength.

A solar cell according to an embodiment of the present invention absorbs light having a broad wavelength ranging from ultraviolet rays to infrared rays, forms two or more electron-hole pairs with one photon, and efficiently converts the electron-hole pairs into currents. Can be.

The solar cell according to an embodiment of the present invention may be utilized as an excellent green energy resource with advantages such as economical manufacturing cost, ease of process, and high efficiency solar energy conversion.

1 is a view illustrating a solar cell according to an embodiment of the present invention.
FIG. 2A is a diagram illustrating the heterojunction quantum dot of FIG. 1. FIG.
FIG. 2B is a band diagram of the heterojunction quantum dots of FIG. 2A. FIG.

Conventional photovoltaic conversion methods of solar cells produce electron-hole pairs that are independent of the energy of photons that are absorbed and are only proportional to the number of photons that are absorbed. Thus, the remaining energy of photons with high energy is lost as heat and is inefficient.

Solar cell technology is changing from the first generation single junction structure to the second generation tandem type multijunction structure. The second-generation tandem multijunction structure is a high efficiency solar cell technology using broadband wavelength absorption.

Recent multiple exciton generation (MEG) solar cells absorb high energy photons to form one electron-hole pair, and the other electrons and holes generated in the excited state transition to a lower energy state Electron-hole pairs can be generated to produce two or more electron-hole pairs.

High-efficiency solar cells absorb light at a broad wavelength from ultraviolet to infrared light, 2) form two or more electron-hole pairs with one photon, and 3) efficiently convert the generated electron-hole pairs into current. Requires to do. Solar cells using heterojunction quantum dots satisfy the above conditions.

Colloidal semiconductor quantum dots made by chemical synthesis are recognized as superior materials in terms of economy, ease, and applicability, and are being applied and industrialized in many fields. Colloidal semiconductor quantum dots can also inexpensively synthesize semiconductor heterojunction structures made of different materials without complicated growth equipment or difficult processes. This heterojunction structure is formed by synthesizing a material in which a band gap is significantly different in one quantum dot. Accordingly, the quantum dot of the heterojunction structure can easily absorb the light of the broadband wavelength. The quantum dots absorb sunlight to form a plurality of electron-hole pairs, which are transferred to the solar cell through a non-radiative resonant transfer process. Thus, the solar cell can operate efficiently.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. However, the present invention is not limited to the embodiments described herein but may be embodied in other forms. Rather, the embodiments disclosed herein are being provided so that this disclosure will be thorough and complete, and will fully convey the concept of the invention to those skilled in the art. In the drawings, the components have been exaggerated for clarity. Portions denoted by like reference numerals denote like elements throughout the specification.

1 is a view illustrating a solar cell according to an embodiment of the present invention.

FIG. 2A is a diagram illustrating the heterojunction quantum dot of FIG. 1. FIG.

FIG. 2B is a band diagram of the heterojunction quantum dots of FIG. 2A. FIG.

1, 2A, and 2B, the solar cell 200 includes a first solar cell 230 including an n-type semiconductor layer 232 and a p-type semiconductor layer 236, and a first solar cell ( And heterojunction quantum dots 202 having a core 210 and a shell 220 surrounding the core 210. The heterojunction quantum dot 202 transfers an electron-electron pair formed by absorbing sunlight to the first solar cell 230 through a poster resonance energy transfer (FRET).

The first solar cell 230 may be a conventional PN junction solar cell. Alternatively, the first solar cell 230 may have a PIN structure further including an intrinsic semiconductor layer (not shown) disposed between the N-type semiconductor layer 232 and the P-type semiconductor layer 236. The P-type semiconductor layer may have a thickness of several nanometers (nm).

The first solar cell 230 receives energy from the heterojunction quantum dot 202 through a poster resonance energy transfer (FRET). The electron-hole pair of the core 210 may transfer energy to the first solar cell 230 through FRET interaction. The first solar cell 230 may obtain energy through a non-radiative resonant transfer process to form an electron-hole pair. Therefore, the current of the first solar cell may flow without directly receiving sunlight. The band gap of the first solar cell should be smaller than the band gap of the core 210.

The first solar cell 230 may be a semiconductor (silicon, germanium, group III-V compound, group II-VI compound) or an organic solar cell.

The first solar cell 230 may include a lower electrode 231, an N-type semiconductor layer 232, a P-type semiconductor layer 236, and an upper electrode 237 that are sequentially stacked. The lower electrode 231 may be in ohmic contact with the N-type semiconductor layer 232. The upper electrode 237 may be in ohmic contact with the P-type semiconductor layer 236.

The upper electrode 237 having a line shape or a pad shape is disposed on the P-type semiconductor layer 236. The heterojunction quantum dots 202 are disposed in an area where the upper electrode 237 is not disposed. The P-type semiconductor layer 236 or the N-type semiconductor layer in contact with the heterojunction quantum dots 202 may be within several tens of nm. Accordingly, electron-electron pairs can reach the PN junction region through non-radiative resonance transfer.

According to a modified embodiment of the present invention, the first solar cell may be PbTe, PbSe, InAs.

According to a modified embodiment of the present invention, the first solar cell may include a lower electrode, a P-type semiconductor layer, an N-type semiconductor layer, and an upper electrode sequentially stacked.

According to a modified embodiment of the present invention, when the first solar cell includes an intrinsic semiconductor layer, the intrinsic semiconductor layer may include Si quantum dots, Ge quantum dots, and In (Ga) As quantum dots.

According to a modified embodiment of the present invention, the first solar cell may include a lower electrode, a P-type semiconductor layer, an intrinsic semiconductor layer, an N-type semiconductor layer, and an upper electrode which are sequentially stacked.

According to an embodiment of the present invention, the first solar cell may be a CuInSe 2 series. The p-type semiconductor layer may be CuInSe 2, and the n-type semiconductor layer may be CdS.

According to a modified embodiment of the present invention, the first solar cell is a group III-V series, the p-type semiconductor layer may be n-type GaAs, the n-type semiconductor layer may be n-type GaAs.

The heterojunction quantum dot 202 may include the core 210 and a cell 220 surrounding the core 210. The core 210 may include a II-VI compound or a III-V compound. The cell 220 may include barrier layers 221 and 223 surrounding at least one pair of the cores 210 and quantum well layers 222 and 224 surrounding the bayer layers 221 and 223. The band gap of the barrier layers 221 and 223 is greater than the band gap of the core 210 and the band gap of the quantum well layers 222 and 24, and the band gap of the quantum well layers 222 and 224 is greater than that of the core 210. It may be larger than the bandgap.

The cell 220 may include a first barrier layer 221 surrounding the core 210, a first quantum well layer 222 surrounding the first barrier layer 221, and the first quantum well layer 222. It may include a second barrier layer 223 surrounding the second barrier layer 223 and a second quantum well layer 224 surrounding the second barrier layer 223. The band gap of the second quantum well layer 224 may be larger than the band gap of the first quantum well layer 222.

Specifically, the core 210 is PbS, the first barrier layer 221 and the second barrier layer 223 is ZnS, the first quantum well layer 222 is CdSe, the second quantum well Layer 224 may be CdS. In this case, an ultraviolet (UV) component or blue component of sunlight is absorbed by the second quantum well layer 224 to form holes in a valence band (VB), and a conduction band (CV). The electrons can be formed in (A1). Subsequently, the electrons may reach the core 210 through the second barrier layer 223, the first quantum well layer 222, and the first barrier layer 221 through tunneling (A2). . In addition, electrons reaching the core 210 may transition to an intermediate energy state. The transition may form an electron-hole pair in the core (A4). In addition, holes in the valence band of the second quantum well layer 224 pass through the second barrier layer 223, the first quantum well layer 222, and the first barrier layer 221 through tunneling. The core 210 can be reached (A5). In addition, electrons in the intermediate energy state of the core 210 may transition to the low energy state (A6). Electrons that transition to the low energy state may form electron-hole pairs in the core (A7).

Photons having UV and blue wavelengths in the light absorbed by the heterojunction structure quantum dots 202 may form two or more electron-hole pairs per one. That is, the heterojunction structure quantum dots may perform multiple exciton generation (MEG).

The green component of sunlight is absorbed by the first quantum well layer 222 to form an electron-hole pair (B1). The electrons may pass through the first barrier layer 221 through tunneling to reach an intermediate energy state of the core 210 (B2). Electrons in the intermediate energy state may transition to the low energy state (B3). The transition may form an electron-hole pair in the core 210 (B5). In addition, holes in the first quantum well layer 222 may reach the core 210 through the first barrier layer 221 through tunneling.

Photons in the infrared band of 1 μm or less, including red, may form electron-electron pairs in the core 210. On the other hand, photons in the infrared band of 1 μm or more are not absorbed by the heterojunction structure quantum dots, and can be irradiated directly to the first solar cell. In this case, the first solar cell may be a II-VI compound, a III-V compound, and a group IV semiconductor and an organic material. The first solar cell can absorb photons in the infrared band of 1 μm or more.

The heterojunction quantum dot 202 may have a plurality of quantum well structures. That is, the quantum well structure may absorb UV, blue, and green in different regions. The core can also absorb infrared light of 1 μm or less, including red. The heterojunction quantum dots 202 may form electron-hole pairs for almost all wavelengths of sunlight. In addition, the heterojunction quantum dots 202 may form two or more electron-hole pairs for UV, blue and / or green.

The electron-hole pair formed by the heterojunction quantum dot 202 may transfer energy to the first solar cell 230 through a poster resonance energy transfer (FRET). Accordingly, the photoelectric conversion efficiency of the first solar cell 230 may be increased. The heterojunction quantum dot may have a PbS / ZnS / CdSe / ZnS / CdS structure. Thus, the heterojunction quantum dots may be synthesized in a quantum dot-quantum well (QD-QW) structure to absorb sunlight from ultraviolet (300 nm) to infrared (1000 nm) region. Photoelectric conversion efficiency of the solar cell according to an embodiment of the present invention can be increased by about 50 percent compared to the conventional solar cell.

The passivation layer 203 may surround the quantum dot 202. The protective film 202 may be used to apply already processed quantum dots on the first solar cell 230. The passivation layer 203 may be trioctylphosphine (TOP) or trioctylphosphine oxide (TOPO).

In order to apply the quantum dot to the first solar cell as a monolayer, a Langmuir-Blodgett deposition (LB) technique and a layer by layer (LBL) technique may be used. The heterojunction quantum dot 202 may be applied as a monolayer on the first solar cell 230. Accordingly, heterojunction quantum dots 202 absorb wideband wavelengths and generate multiple electron-hole pairs through the MEG. The generated electron-hole pair is delivered to the first solar cell 230 via FRET.

The surface of the first solar cell 230 to which the heterojunction quantum dot 202 is applied may have a shape such as a pyramid. Accordingly, the surface area to which the heterojunction quantum dot 202 is applied may be increased. In addition, sunlight reflected or scattered from the surface of the first solar cell 230 may be reabsorbed to increase light efficiency.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it is to be understood that the invention is not limited to the disclosed exemplary embodiments, And all of the various forms of embodiments that can be practiced without departing from the technical spirit.

202: quantum dots
230: first solar cell
210: core
220: cell

Claims

A first solar cell including an N-type semiconductor layer and a P-type semiconductor layer; And
A heterojunction quantum dot disposed on the first solar cell and having a core and a shell surrounding the core;
The heterojunction quantum dot absorbs sunlight and transfers an electron-electron pair formed to the first solar cell through Poster resonance energy transfer (FRET),
The cell is:
A first barrier layer surrounding the core;
A first quantum well layer surrounding the first barrier layer;
A second barrier layer surrounding the first quantum well layer; and
A second quantum well layer surrounding the second barrier layer,
The band gap of the second quantum well layer is larger than the band gap of the first quantum well layer.

The method of claim 1,
The core comprises a Group II-VI compound or a Group III-V compound,
The bandgap of the first barrier layer is greater than the bandgap of the core and the first quantum well layer,
The band gap of the first quantum well layer is larger than the band gap of the core.

delete

The method according to claim 1,
The core is PbS,
The first barrier layer and the second barrier layer is ZnS,
The first quantum well layer is CdSe,
The second quantum well layer is a solar cell, characterized in that the CdS.

5. The method of claim 4,
The first solar cell is a group III-V compound, a group IV semiconductor, and an organic material, characterized in that the solar cell.

The method according to claim 1,
The first solar cell is:
Further comprising an intrinsic semiconductor layer disposed between the N-type semiconductor layer and the P-type semiconductor layer,
The intrinsic semiconductor layer includes a Si quantum dot, a Ge quantum dot, an InAs quantum dot, or an InGaAs quantum dot.

The method according to claim 1,
The N-type semiconductor layer or the P-type semiconductor layer is disposed in contact with the heterojunction quantum dot,
The N-type semiconductor layer or the thickness of the P-type semiconductor is a solar cell, characterized in that several nanometers (nm).

The method according to claim 1,
And a protective film surrounding the quantum dots,
Wherein a band gap of the first solar cell is smaller than a band gap of the core.