All-polymer solar cells (all-PSCs) based on p-type polymer as electron donor and n-type polymer as electron acceptor attracts a lot of attention because of its advantages of easy tuning of optical and electrical properties of polymer and mechanical stability of the all polymer blend compared to polymer solar cells (PSCs) based on fullerene derivative as electron acceptor. However, the power conversion efficiency (PCE) of all-PSCs still is lower than that of PSCs based on fullerene derivative. Their poor device performance accounts for lower electron mobility of polymer acceptor than that of fullerene derivatives. In addition, the anisotropic charge transport of polymer acceptor depending on their polymer packing geometry in thin films more significantly affects the charge collection efficiency of all-PSCs than that of PSCs based on fullerene derivative, which shows isotropic charge transport property. Therefore, the development of polymer acceptor which possess superb electron transport capability is urgent. Herein, we fabricated high-performance all-PSCs without any solvent additives or thermal treatments by using a series of naphthalene diimide (NDI)-based alternating copolymers as electron acceptors. We found that the high electron transport ability of the polymer acceptor is one of the most important requirements for producing high-performance, additive-free all-PSCs. To control the planarity of the polymer backbone and optimize electron mobility, we introduced three different electron-rich units (i.e., thiophene (T), bithiophene (T2), and thienylene-vinylene-thienylene (TVT)) into the NDI-based polymers. Particularly, P(NDI2OD-TVT) polymers exhibited the highest electron mobility (2.31 cm2 V-1 s-1) in organic field effect transistors due to the enhanced degree of coplanarity. Also, the high electron mobility of P(NDI2OD-TVT) facilitated electron transport in all-PSC blends, resulting in the well-balanced hole/electron mobility ratio. Thus, all-PSCs based on P(NDI2OD-TVT) acceptor exhibited the high efficiency of 4.25% without any solvent additives or thermal treatments.

Additive-free, high-performance ,all-polymer solar cells based on naphthalene diimide-based polymer acceptor with high-electron mobility

251st National Meeting (2016)

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.