Matthew J. Panzer1, Alexi C. Arango2, Tim P. Osedach2, Scott M. Geyer3, Moungi G. Bawendi3, and Vladimir Bulovic2. (1) Research Laboratory of Electronics, Massachusetts Institute of Technology, Room 13-3082, 77 Massachusetts Avenue, Cambridge, MA 02139, (2) Electrical Engineering & Computer Science, Massachusetts Institute of Technology, (3) Chemistry, Massachusetts Institute of Technology
Colloidal quantum dots (QDs) are of great interest for next generation photovoltaic (PV) device architectures because of their amenity to large scale solution-based synthesis and processing techniques, as well as tunability of the QD bandgap with its size. As an early step towards realizing a low-cost, entirely printed PV platform, we investigated a hybrid device structure in which thin films of CdSe QDs are deposited onto an organic hole transport layer via microcontact printing using a polydimethylsiloxane (PDMS) stamp. Control of QD film morphology by adjusting the surface energy of the PDMS stamp showed a significant improvement in the open circuit voltage of the device. In addition, chemical treatment of the QD films in situ on stamps was used in an effort to improve carrier transport through the QD film in the completed PV device by exchanging the bulky native trioctylphosphine (TOP) ligands for several amines with shorter molecular lengths. Solar cells with optimized QD layers achieved open circuit voltages of 1.3 V and short circuit currents of nearly 0.1 mA/cm2 under green light illumination (78 mW/cm2; peaked at 532 nm). An internal quantum efficiency of ~30% was also obtained (external quantum efficiency ~0.5%). Further improvements to our hybrid device architecture are currently under investigation, including the possibility of using a multilayer tandem structure.