基于热活化延迟荧光材料的有机肖特基结光伏电池的介电特性基础研究

The organic Schottky photovoltaic cell (OPV), a novel structure firstly reported in 2011, has received wide interest because of its simple cell architecture and ultrahigh photocurrent. The related investigation of the physical mechanism mainly focuses on the formation of high open circuit voltage and the hole-transport model. There are limited reports about the application of thermally activated delayed fluorescence (TADF) materials that possess long exciton-lifetime on OPVs, and about the influence of dielectric properties on OPV device performance. Aiming at this problem, the subject investigated in the project centralizes on the organic Schottky junction including small amount of TADF donor. The project reveals the regulation mechanism of photo-generated carrier and molecule structure of TADF homologues on the dielectric property of donors/acceptors and organic Schottky junctions, and its influence on the space charge distribution, build-in potential, and device performance. We primarily investigate the change of the static dielectric property of donor/acceptor and the device capacitance in dark and under the various illumination, and build a model how the dielectric property of donor/acceptor modulate the exciton dissociation and recombination, carrier long-range transfer, charge accumulation, and the delocalization of charge transfer states in Schottky junctions. The device performance will be further improved by the application of novel donors/acceptors, such as the composite of perovskite and TADF donor, the new acceptor which is traditionally used as donor, etc., and by the modification of device structures. The project would help to direct the design of novel photovoltaic materials and the improvement of cell structures.

2011年首次报导的有机肖特基结光伏电池因其结构简单且呈现出超高光电流引起国内外的广泛关注。其相关物理机理研究主要集中在高开路电压形成机理及空穴传输模型的探讨，关于具有长激子寿命的热活化延迟荧光(TADF)材料在肖特基结中的应用，及给/受体介电特性对电池性能的影响并无深入研究。针对这一现状，本项目以含有超低TADF给体浓度的有机肖特基结电池为研究对象，探索光生载流子和TADF给体同系物的空间结构对材料和器件的介电特性的调控，及其影响空间电荷分布、内建电场与电池性能的规律。重点研究肖特基结中给/受体稳态介电特性与相应器件电容在暗条件和不同光照强度下的变化，建立材料介电特性对肖特基结中激子分离与复合、载流子长程传输、电荷富集和电荷转移态离域的调控模型。通过新材料如钙钛矿和TADF给体复合膜、给体用作受体等的应用和结构改善进一步提升电池性能。本项目将为新给/受体分子设计和器件结构优化提供思路。

2011年首次报导的有机肖特基结光伏电池因其结构简单且呈现出超高光电流引起国内外的广泛关注。其相关物理机理研究主要集中在高开路电压形成机理及空穴传输模型的探讨，关于具有长激子寿命的热活化延迟荧光(TADF)材料在肖特基结中的应用，及给/受体介电特性对电池性能的影响并无深入研究。针对这一现状，本项目制备了一系列基于超低浓度TADF发光材料为给体的有机肖特基结电池，探索了光生载流子和TADF给体同系物的空间结构对材料和器件的介电特性的调控，及其影响空间电荷分布、内建电场与相应电池性能的规律。重点研究了基于红光染料DBP和DIP的肖特基结中给/受体稳态介电特性与相应器件电容、电荷密度、耗尽区宽度在暗条件和光照下的变化。另外比较研究了基于类似LUMO能级的受体C60和C70，PTCBI和PTCDI的肖特基结的介电特性。基于一系列绿光TADF材料4CzPN，4CzIPN和4CzTPN制备了C60肖特基结，发现这些强发光材料并不能显著提升纯C60肖特基结的电池性能。根据这些结果，建立材料介电特性对肖特基结中激子分离与复合、载流子长程传输、电荷富集和电荷转移态离域的调控模型。此外，通过将具近红外吸收的给体DBP，SubPc等作为受体制备了不同结构太阳能电池，发现其显著改善电池的Voc，且适当浓度的掺杂受体层能进一步提升Jsc。掺杂空穴传输层PEDOT:PSS有效提升了基于PDPP3T肖特基结电池的性能。最后探索了钙钛矿太阳能电池的介电特性。本项目的研究成果将为新给/受体分子设计和器件结构优化提供思路。