Highly Efficient Polymer Solar Cells Based On Composite Modification Of ZnO/carbon Quantum Dots

With the developing and progressing of human society,using non-renewable fossil fuels has brought about increasingly serious problems such as environmental pollutions and energy crisis.Therefore,the clean energy,such as wind energy and solar energy,has attracted widespread attention.Polymer solar cells?PSCs?are considered as one of the promising renewable energy technologies due to the unique advantages of high absorption characteristics in the visible-light region and solution-process capability for large-area low-cost flexible PSCs.To date,significant progresses have been made in the research of PSCs,and the conversion efficiency of single-junction polymer solar cells has exceeded 14%.In PSCs,apart from the continuous development of narrow-bandgap donor materials and non-fullerene acceptor materials,the interfacial modification has a very important significance for the improvement of conversion efficiency,and has become a hot topic of research.In this dissertation,firstly,the photovoltaic performances are compared in traditional and inverted structure devices.Then,in the inverted PSCs using ZnO as the electron extraction layer?EEL?,the influence of the introduction of carbon quantum dots?C-QDs?on the polymer solar cell was studied,and the reason was systematically analyzed to make a reasonable explanation.Its universality was also investigated.The specific work is as follows:?1?In the second chapter,the thickness of the active layer and the thickness of the ZnO EEL in the inverted structure device are optimized in the P3HT:PC₆₁BM-based PSCs.Then the performances of device with intraditional and inverted structures are compared and analyzed,and a reasonable explanation is given.Consequently,the inverted device structure is selected as the device structure in subsequent studies.?2?In the third chapter,water-soluble C-QDs interlayer was inserted into an inverted structure PSCs,which using ZnO as the EEL and P3HT:PC₆₁BM as the active layer.The goal is to improve the performance of PSCs.And the thickness of the C-QDs interlayer is systematicallyoptimized.Our results have proved that the introduction of C-QDs interlayer can passivate the surface defects of ZnO and improve the contact quality at the interface of ZnO and P3HT:PC₆₁BM active layer,which can promote the exciton separation and charge extraction efficiency in PSCs.At the same time,the C-QDs interlayer can effectively suppress exciton quenching at the interface between Zn O and P3HT:PC₆₁BM active layer,and reduce the internal charge carrier recombination loss.Finally,the short-circuit current density(J_sc)increased from 10.50 mA cm^-2 to 13.30 mA cm^-2,and the power conversion efficiency?PCE?increased from 3.78%to 4.85%.?3?In the fourth chapter,in order to prove the universality of ZnO/C-QDs composite EEL in PSCs,we applied it into PTB7:PC₇₁BM system.It was proved that the performance parameters of the open-circuit voltage(V_oc),J_sc,and the fill factor?FF?of the device were simultaneously improved.The PTB7:PC₇₁BM-based polymer solar cell exhibited excellent performance,possess a significant improvement in PCE of?9.64%,which is>27%higher than that of a control cell??7.59%?.Ultimately,ZnO/C-QDs composite EEL shows excellent universality in PSCs.