Research Projects

Organic phototransistors (OPTs) have gained global attention due to their promising benefits, including cost-effectiveness, lightweight design, exceptional flexibility, and the capability for broadband detection. Wearable electronics must meet physical flexibility and robustness requirements beyond inorganic or small molecule based photosensors. In this regard, conjugated polymers are the most stretchable solution-processable semiconductor for super flexible devices because of their excellent rheological properties. Conjugated polymer films are extremely smooth and can be solution-processed at room temperature. As we know that high mobility is crucial for the OPTs performance to enable faster carrier transport, efficient charge collection, and reduced transit time, leading to high photocurrent. Despite the remarkable effort in the recent years in field-effect mobility obtained in polymer-based organic transistors, the design and performance of polymer-based OPTs are still poor. Since donor-acceptor (D-A) heterojunction-based OPTs offer enhanced light absorption, efficient charge separation and transport, but the fabrication of D-A-based bi-layered heterojunction of conjugated polymers are difficult to fabricate due to the unavailability of orthogonal solvents. Bulk-heterojunction (BHJ) based OPTs are more popular due to ease of fabrication, and most of the BHJ-based OPTs are prepared by single-step spin coating where polymers are isotropic and their poor film morphology results in low mobility, limiting the performance of the resulting OPTs. The sientific objective of this project is to create high-performance ultrathin heterojunction-based OPTs using our novel film fabrication strategy. Here, we aim to solve the existing problems in polymer-based OPTs by a new kind of solution-processable fabrication technique with oriented polymers using unidirectional floating-film transfer method (UFTM). The UFTM is developed by the applicant, is a solution-processed R2R-compatible fabrication method that produces highly uniform and oriented polymer films. The method enables the fabrication of both bi-layered donor-acceptor (D-A) films and bulk-heterojunction (BHJ) films with unidirectionally aligned polymers. These polymer orientations facilitate improved charge transport, higher photocurrent, and enhanced sensitivity. The scientific objectives is to develop and optimize the UFTM for layer-by-layer and BHJ film fabrication with oriented then fabrication and evaluation of high-mobility D-A bi-layered and BHJ-based OPTs. In last we also aim to demonstrate the potential of these devices in light-sensitive logic circuits. Successful implementation will overcome fabrication challenges in CP-based OPTs, advance fundamental understanding of oriented polymer film, and establish India as a leader in flexible phototransistor research. The outcomes promise significant implications for flexible electronics and optoelectronics applications.