Photoinduced Degradation Studies of Organic Solar Cell Materials Using Kelvin Probe Force and Conductive Scanning Force Microscopy

Abstract

We investigated the photoinduced changes in the surface potential and conductivity for locally degraded active layers of organic solar cell materials using electrical modes of scanning force microscopy. Samples were degraded under different partial pressures of oxygen and humidity in the presence of light. Degraded and nondegraded areas were investigated by Kelvin Probe Force Microscopy (KPFM) and conductive scanning force microscopy (cSFM). The analysis allowed us to quantify the extent of degradation and compensate the contribution of the probe tip. Two typical blends used for organic solar cell, i.e., P3HT:PCBM and PCPDTBT:PCBM, were investigated. We observed that P3HT:PCBM photodegraded significantly more than PCPDTBT:PCBM for an environment containing oxygen. For short photodegradation times (1 h), we verified that changes in the surface potential and conductivity of P3HT:PCBM films were fully reversible after annealing. For individual layers of P3HT and PCBM, we found that only P3HT degrades. However, the blend material of P3HT and PCBM leads to an accelerated degradation supporting the interpretation that PCBM undergoes a series of oxidations in the blend.

Charge transport and its characterization using photo-CELIV in bulk heterojunction solar cells

“…The issue of degradation in polymer solar cells is complex owing to the plethora of degradation pathways that occur within the many layers comprising the device architecture. Significant literature can be found on this problem, including some excellent reviews and the identification of numerous factors such as oxygen, water, light, heat and mechanical stresses as some of the crucial degradation triggers. The decline in photovoltaic performance with time is largely due to the combined action of interrelated parallel mechanisms at different locations of the device, with specific kinetics.…”

Air-processed active-layer of organic solar cells investigated by conducting AFM for precise defect detection

“…19,20 Particularly, conducting AFM has already been introduced to study the degradation of active layer from conjugated polymer and PCBM blend by varying environmental condition. 21 In addition to the environmental elements, the presence of solvent vapors during fabrication process steps or even the way of characterizations done can affect the device performance considerably. But it is already reported that the long-term stability is an issue when using PEDOT:PSS as HTL due to the instability of the strongly hygroscopic counterpart poly-(styrene sulfonate) which dissociates under the inuence of moisture in the air.…”

A DFT/TDDFT mission to probe push–pull vinyl coupled thiophene oligomers for optoelectronic applications

“…The design and development of renewable energy sources using organic solar cells (OSC) have attracted considerable interest in recent years due to increasing energy demand. [1][2][3][4][5][6][7] Owing to their large surface areas and porous structures, metal organic frameworks (MOF) and covalent organic frameworks (COF) have been the subject of research in the areas of gas storage and catalysis. [8][9][10][11][12] Quantum chemical calculations have been used to understand not only the nature of MOFs/COFs (both in the ground and excited states) but also the character of their bands.…”