Molecular and Morphological Influences on the Open Circuit Voltages of Organic Photovoltaic Devices

Abstract

We explore the dependence of the dark current of C(60)-based organic photovoltaic (OPV) cells on molecular composition and the degree of intermolecular interaction of several molecular donor materials. The saturation dark current density, J(S), is an important factor in determining the open circuit voltage, V(oc). The V(oc) values of OPVs show a strong inverse correlation with J(S). Donor materials that show evidence for aggregation in their thin-film absorption spectra and polycrystallinity in thin film X-ray diffraction result in a high dark current, and thus a low V(oc). In contrast, donor materials with structures that hinder intermolecular pi-interaction give amorphous thin films and reduced values of J(S), relative to donors with strong intermolecular pi-interactions, leading to a high V(oc). This work provides guidance for the design of materials and device architectures that maximize OPV cell power conversion efficiency.

The isotopic effects of deuteration on optoelectronic properties of conducting polymers

“…Recent studies show that V oc is proportional to the energy of the interfacial charge transfer state 34,43 . We note that the formation of an interfacial charge transfer state can be detected from subband absorption, photoluminescence, electroluminescence and magnetic field measurements [34][35][36][37][38][39][40][41][42][43][44] . The electroluminescence emission from the protonated and deuterated P3HT/PCBM blend (Fig.…”

“…5. Based on the generalized Shockley equation under open circuit conditions, V oc is given as [40][41][42] ,…”

Charge transport and exciton dissociation in organic solar cells consisting of dipolar donors mixed withC70

“…[23][24][25][26][27] In steady-state, the J-V characteristics are governed primarily by polaron-pair and free charge recombination dynamics at the D-A junction. 23 Thus:…”

Energy-Level Alignment at Metal–Organic and Organic–Organic Interfaces in Bulk-Heterojunction Solar Cells

“…However, if the off-set between the donor and acceptor levels is too large, substantial energy loss occurs and the overall power conversion efficiency of the cell will suffer [6]. The importance of the organicorganic heterojunction is further enforced by the recent results where weak ground state interactions between donor polymers and acceptor fullerenes leading to charge transfer (CT) complexes are shown to control the open circuit voltage, V oc , of the cells [7][8][9][10][11].…”