The absorption measurements were carried out with a Cary 5000 UV-Vis-NIR spectrophotometer (Agilent Technologies; slit height: full; spectral bandwidth: 2 nm). The electrical properties were measured by Hall effect measurements (HMS-7000, Ecopia), with a magnetic field of 0.55 T and an operating current of 15 mA. SEM measurements were performed using a Hitachi SU 8030 (see Figure ). The approximate height of the PbS thin films was determined with a Bruker Dektak XT-A stylus profilometer with a stylus force of 3 mg, a stylus scan range of 6.5 µm and stylus radius of 2 µm (see Figure ).