Revisiting the Classical Wide-Bandgap HOMO and Random Copolymers for Indoor Artificial Light Photovoltaics

Area of Science:

• Materials Science
• Organic Electronics
• Renewable Energy

Background:

• Organic indoor photovoltaics (IPVs) offer lightweight, flexible energy harvesting for low-power devices and IoTs.
• Matching IPV absorption spectra to indoor light sources (400-700 nm) is crucial for high power density.
• Classical polymer donors like PBDTT have wide bandgaps and deep HOMO levels, requiring modification for optimal indoor light absorption.

Purpose of the Study:

• To develop efficient photoactive materials for organic indoor photovoltaics (IPVs).
• To fine-tune the absorption range of polymer donors to match indoor light spectra.
• To establish molecular design guidelines for high-performance IPVs.

Main Methods:

• Synthesized benzo[1,2-b:4,5-b']dithiophene-based homopolymer (PBDTT) as a polymer donor.
• Created random copolymers by incorporating thieno[3,4-c]pyrrole-4,6,-dione (TPD) as a weak electron acceptor unit into PBDTT.
• Varied TPD composition to optimize polymer absorption spectra, specifically creating B30T70 with 70% TPD.

Main Results:

• The polymer B30T70, with 70% TPD, demonstrated absorption covering the full spectrum of indoor light sources (LEDs, fluorescent lamps).
• Organic IPVs fabricated with B30T70 blended with PC71BM achieved a significant power conversion efficiency (PCE) of 18.3% under indoor lighting.
• A dramatic enhancement in PCE was observed, increasing from 6.0% under 1-sun conditions to 18.3% in an indoor environment.

Conclusions:

• Tailoring polymer donor absorption to indoor light spectra is key for high-efficiency IPVs.
• The developed B30T70 polymer and its molecular design provide a promising pathway for efficient organic IPVs.
• Simple molecular design guidelines can lead to the development of advanced photoactive materials for sustainable indoor energy harvesting.