Low-light characteristics of polymer photocell with S-shaped current-voltage curve at 1 sun

ABSTRACT

The S-shaped current-voltage characteristic is a sign of poorly performing organic photocell, since it gives low fill-factor. In this paper, the characteristics of a bulk heterojunction device with PTB7-Th:C₇₀ composite without thermal annealing, which shows S-shaped current-voltage curve with the power conversion efficiency (PCE) of 1.5% under AM 1.5G 1 sun illumination, under low light illumination are studied. It is found that the current-voltage characteristic of the device under 10⁻³ sun illumination does not show the kink and thus the PCE exceeds 5%. A photocell which shows both S-shaped and normal current-voltage characteristics seems to be rarely reported so far.

KEYWORDS:

• Organic photocell
• bulk heterojunction composite
• unmodified fullerene
• S-shaped characteristic
• indoor light harvesting

Funding

This work was partially supported by JSPS KAKENHI under Grant Number JP26289094.