The transition toward sustainable energy systems requires scalable materials and device architectures that efficiently convert abundant solar energy into chemical energy in the form of solar fuels. Solution-processable semiconductors offer a compelling pathway toward low-cost, large-area solar energy conversion. However, significant challenges remain in simultaneously achieving precise materials engineering, scalable fabrication, and high-performance device integration. This thesis addresses these challenges by developing printable semiconductor nanomaterials and solution-processed Z-scheme photocatalyst (PC) sheets for solar-driven overall water splitting. The first chapter of this thesis establishes a scalable powder-based solution-processing strategy for synthesizing the complete compositional series of two-dimensional SnSxSe(2-x) alloy nanosheets. By systematically varying the sulfur-to-selenium ratio, the optical bandgap, in-plane electrical transport, and out-of-plane conductivity are tuned across a wide parameter space. The resulting alloy library provides a versatile platform for application-specific materials optimization, with photoelectrochemical studies demonstrating how the interplay between optical absorption and charge transport governs device performance. Building on solution-process methods, the second chapter of the thesis develops a scalable fabrication strategy for Z-scheme PC sheets capable of unbiased solar-driven overall water splitting (OWS). A fully solution-process-based microdomain templating approach is introduced to integrate inorganic BiVO4 oxygen-evolution domains with organic semiconductor (OS) bulk heterojunction (BHJ) hydrogen-evolution domains on a single substrate. This hybrid architecture demonstrates unassisted OWS under simulated solar illumination while establishing a scalable manufacturing route for PC sheet fabrication. The final chapter extends this concept by demonstrating an all-organic PC sheet architecture. Through charge-extraction underlayer engineering, a single OS BHJ is shown to function as either a photocathode or photoanode depending solely on the selected molecular underlayer contact. Following optimization of the individual half-reactions, both functionalities are integrated into a Z-scheme PC sheet. The resulting device achieves stable, unbiased solar-driven OWS, demonstrating the feasibility of fully organic PC sheets as a scalable platform for solar fuel generation. Collectively, this thesis advances solution-processable semiconductor technologies from fundamental materials engineering to integrated device architectures. By combining compositionally tunable printable nanomaterials with scalable strategies for fabricating photocatalyst sheets, this work establishes new design principles for solar energy conversion systems and provides a foundation for the future development of low-cost, scalable technologies for sustainable hydrogen production.