Organic Semiconductor Thin Film Crystal Growth: Formation and Propagation

Organic semiconductors are commercially validated regarding OLED displays, with considerable scope for future applications. Toward these future prospects, I will present recent work from our group that seeks to better understand how to form crystalline films of organic semiconductors, approaching single-crystal-devices, but in a thin film platform. Through proper control of processing, we are able to realize pinhole free organic semiconductor films with single crystal grains with millimeter dimensions. We have found that transport in these films is considerably improved compared to disordered films, and that organic solar cells incorporating these long-range-ordered films exhibit highly delocalized and band-like charge transfer (CT) states, contributing to noticeably lower energy losses. We will discuss these aspects and our understanding to-date of which molecules are amenable to the formation of such films, and how to propagate crystal growth both homoepitaxially and heteroepitaxially.