Enhanced cyanine solar cell performance upon oxygen doping (Organic Electronics 9 (2008) 85–94)

Abstract

The effect of exposing cyanine-fullerene C 60 bilayer solar cells to ambient atmosphere is investigated. For exposure times of a few hours and concomitant light soaking, the device performance experiences a drastic power efficiency increase going from 0.14% to 1.2% measured at 30 mW/cm 2 simulated solar irradiation. The 10-fold enhancement is attributed to the photoinduced doping involving oxygen and water leading to the formation of reactive superoxide anions and mobile holes in the cyanine layer. The influence of water and dry oxygen are investigated separately. While water deteriorates the device performance, dry oxygen leads only to a partial increase of efficiency. Annealing does not ameliorate the performance of doped devices. Although then the cyanine layer features more crystallinity, the considerable morphological changes cause diffusional loss in charge carrier collection. Doping of not annealed devices brings a sizeable efficiency enhancement that highlights the importance of charge carrier transport in cyanine dye based solar cells.

Nanoscale Structuring of Semiconducting Molecular Blend Films in the Presence of Mobile Counterions

“…PCBM is one of the best known electron acceptors in heterojunction organic solar cells, and PCBM domains strongly suggested to originate from a similar liquid−liquid dewetting mechanism have been observed during phase separation of polythiophenes and PCBM . In addition, already a strict bilayer of CyC and C 60 has been demonstrated to function well as a photovoltaic device . An understanding of the underlying domain formation processes is of crucial importance for the performance increase of such organic thin-film devices.…”

“…54 In addition, already a strict bilayer of CyC and C 60 has been demonstrated to function well as a photovoltaic device. 55 An understanding of the underlying domain formation processes is of crucial importance for the performance increase of such organic thinfilm devices.…”

A “Cyanine−Cyanine” Salt Exhibiting Photovoltaic Properties

“…On the other hand, their exceptional absorption properties have been used in the field of materials science (nonlinear absorbing materials, hybrid solar cells, etc.). More recently, organic photovoltaic has appeared as a new field of application for these light-harvesting molecules . After 16 years of intensive studies, bulk heterojunction (BHJ) organic solar cells based on poly(3-hexylthiophene) (P3HT) and [6,6]-phenyl-C61-butyric acid methyl ester (PCBM) have reached around 5% of power conversion efficiency (PCE) .…”

“…For the 3 :[60]PCBM blend system we found the optimal blend ratio of 1:2. For this device, the PCE was found to be 0.4%, which is, to our knowledge, one of the best results obtained for a cyanine-based photovoltaic device …”