Material Synthesis And Device Structure Design For Flexible And Semitransparent Functional Organic Solar Cells

The power conversion efficiency(PCE)of organic solar cells(OSCs)has grown rapidly in recent years,and their advantages,such as solution processing and low cost have attracted tremendous attentions.Importantly,the flexible and semitransparent OSCs allow them to have unique advantages for industrialization in terms of light weight,flexibility,transparency and roll-to-roll mass production.In laboratory,the highest PCE of flexible OSCs has reached 12.5%,and that of semitransparent organic solar cells(ST-OSCs)also exceeded 11%.To realize the application in the wearable energy equipment and building-photovoltaic-integration,the device performance of flexible and semitransparent OSCs needs to be further improved.Thus,this thesis designs and synthesizes high-performance electron transporting layer(ETL)materials which are suitable for flexible substrates to improve the bending durability of flexible devices.In addition,the transmitted light of ST-OSCs was precisely controlled using absorption complementary characteritics of ternary photoactive layer and dielectric mirror to improve their color rendering and photovoltaic performance.The main results are as follows1.An n-type self-doping fullerene electrolyte PCBB-3N-3I was synthesized as an ETL material for the application in OSCs.It can be processed at room temperature,and shows high conductivity,appropriate energy levels,thickness-insensitive and excellent mechanical properties.Moreover,PCBB-3N-3I ETL functions as light-harvesting acceptor in the bilayer solar cell,which contribute part of the photocurrent.As a result,the PCBB-3N-3I ETL-based inverted OSCs with PTB7-Th:PC71BM as photoactive layer demonstrate a PCE of 10.04%,which is comparable to that of rigid device.It was one of the highest PCEs of flexible OSCs reported at the end of 2018.More importantly,the flexible device can maintain 95.6%of the initial efficiency after 1500 bending cycles,it revealed that the organic semiconductor ETL material was beneficial to improve the mechanical flexibility of flexible OSCs.2.A synergistic effect is first proposed by employing a dielectric mirror and ternary photoactive layer with near-infrared absorption to tune the color perception of ST-OSCs.As a result,a neutral-color ST-OSC with high average transmittance of over 21%has been successfully constructed,and a remarkable color-rendering index approaching 100 and high PCE of 9.37%are simultaneously achieved,which is the highest PCE reported for neutral-color ST-OSCs to date.Importantly,this synergistic effect is demonstrated to be a universal strategy that is not only suitable for various photoactive layer systems,but can also be implanted in flexible substrate.The resulting neutral-color flexible ST-OSCs also show a promising PCE of 8.76%,which promoted the development of flexible semitransparent OSCs.