The Application Of One-dimensional Photonic Crystals In Semitransparent Polymer Solar Cells

With scientific and technological progress and living standard improvement, the application of solar cells is already not focus on power generation. In last decade,building integrated photovoltaic(BIPV) have becoming a novel application of solar energy. Then,the semitransparent solar cells are arising due to the feature of power generation and transparent. The semitransparent polymer solar cells(STPSCs) have been considered as an attractive area of research due to desirable features of light weight, flexibility, low cost and easy fabrication process. It can apply on portable electronics, outdoor products, automobile and stereoscopic agriculture greenhouse. Compared to the inorganic semitransparent solar cells, the STPSC can apply on the building. It brings the fresh impact on photovoltaic industry and becoming the most promising semitransparent solar cells.Currently, one of the investigations of STPSC is focus on settle the two contradictory characteristics, that is, power conversion efficiency(PCE) and transparency. Another important investigation is color render property of STPSC. Around the research topics and on the bases of experiment and simulation of STPSC, we proposed an effective method to settle the two challenges of STPSC field simultaneously. This method is introducing the one-dimensional photonic crystals(1DPC) onto STPSC. Firstly, we designed the photonic bandgap of 1DPC corresponding to the strong absorption range of active layer. The incident light will reflected back into the active layer then increase the absorption. At the same time,the other light can also transmit though the STPSC device to ensure the transmittance. The novel designation solves the problem of contradiction of PCE and transmittance effectively.Then, we designed the photonic bandgap of 1DPC corresponding to the weak absorption range of active layer. It can also reflect the incident light back into the active layer. But this part of reflect light can balance the transmittance spectrum of STPSC device. An enhanced color render index(CRI) STPSC is achieved by decrease the fluctuation of transmittance spectrum. In this dissertation, we verified the structure designation of STPSC/1DPC with four active layers, P3HT:PC60BM, P3HT:IC60BA, PSBTBT:PC60BM and PCDTBT:PC70BM.Firstly, for the P3HT:PC60BM active layer STPSC, the center wavelength of 1DPC is designed as 520 nm. This photonic bandgap of 1DPC is corresponding to the strong absorption range of P3HT:PC60BM. It can reflect the incident light back into the active layer then increase the absorption and the PCE. And, the other light can also transmit though the STPSC device to ensure the transmittance and satisfy the transparent requirement of STPSC. For the device with 8 pairs of 1DPC, the PCE is improved from2.04% to 2.58%. It also has a higher average transmittance about 40% in the wavelength range of 600–780nm.Secondly, with higher open circuit voltage(Voc), the P3HT:IC60BA active layer STPSC,we designed two 1DPCs. The photonic bandgap of the first 1DPC is 520 nm which is corresponding to the strong absorption range of P3HT:IC60BA. It is used to increase the absorption and the PCE. For the device with 8 pairs of 1DPC, the PCE is improved from3.32% to 4.12%. It also has a higher average transmittance about 34% in the wavelength range of 380–780nm. The photonic bandgap of another 1DPC is 680 nm which is used to improve the CRI. Here, the 1DPC is corresponding to the weak absorption range of active layer. The reflect light of 1DPC can balance the transmittance spectrum of STPSC device.An enhanced color render index(CRI) STPSC is achieved by decrease the fluctuation of transmittance spectrum. Meanwhile, it can also reflect a little incident light back into the active layer and improve the PCE weakly. With 4 pairs of 1DPCs, under AM 1.5G illumination, the CRI is increased from 78 to 91, the chromaticity difference(DC) is decreased from 0.0270 to 0.0035, the PCE is enhanced from 4.14% to 5.01%, and the average transmittance of 380–780nm is decreased from 39.0% to 26.7%. We can found thatthe improvement of CRI and PCE is achieved by sacrificed the transmittance. Because the application requirement of transmittance of STPSC is 25%, the STPSC with 1DPC can still satisfy.Thirdly, for the STPSC with PSBTBT:PC60BM active layer, we also designed two1 DPCs. The photonic bandgap of the first 1DPC is 680 nm which is corresponding to the strong absorption range of PSBTBT:PC60BM. It is used to increase the absorption and the PCE. For the device with 8 pairs of 1DPC, the PCE is improved from 1.92% to 2.46%. It also has a higher average transmittance about 40% in the wavelength range of 380–580nm.The photonic bandgap of another 1DPC is 520 nm which is used to improve the CRI. With3 pairs of 1DPCs, under AM 1.5G illumination, the CRI is increased from 77 to 91, the DC is decreased from 0.0308 to 0.0045, the PCE is enhanced from 3.43% to 4.01%, and the average transmittance of 380–780nm is 32.99%.Finally, for the STPSC with PCDTBT:PC70BM active layer, we designed three 1DPCs to further verify the influence of 1DPC to STPSC. The photonic bandgap of the first 1DPC is550 nm which is corresponding to the strong absorption range of PCDTBT:PC70BM. It is used to increase the absorption and the PCE. For the device with 8 pairs of 1DPC, the PCE is improved from 4.24% to 5.16% and the average transmittance of 380–780nm is 29.3%.The photonic bandgap of second 1DPC is 450 nm which is used to improve the IPCE of the light in relative weak absorption range(<500nm) of PCDTBT:PC70BM. For the device with8 pairs of 1DPC, the PCE is improved from 4.24% to 4.84% and the average transmittance of 380–780nm is 32.5%. The photonic bandgap of third 1DPC is 730 nm which is used to improve the CRI. In order to testify the universality of improvement of CRI, in the calculation of CRI, we used three light sources, the common used AM 1.5G illumination light source, the daylight representation standard illuminant D65, and the tungsten lamp representation standard illuminant A. With 5 pairs of 1DPCs, the CRI is increased from 97,95 and 96, respectively. The excellent CRI demonstrates that our structure designation is very successful. For different light source, our device also exhibit high CRI and maintain the light property of light source. Meanwhile, the PCE is enhanced from 4.87% to 5.31%,and the average transmittance of 380–780nm is 25.1%.In conclusion, we successfully introduce the 1DPC onto the STPSC devices with four active layers, P3HT:PC60BM, P3HT:IC60BA, PSBTBT:PC60BM and PCDTBT:PC70BM.We settle the two problems of STPSC field by designed different center wavelength of1 DPCs for different active layers. Hence, the method proposed in this dissertation offers an effective scientific basis of SPTSC widely production and application. It is the key technology to solve the problem of STPSC field. The method is too significant. The experiment and theory conclusions of this dissertation proposed a solid foundation for widely application of STPSC.