Semiconductor lasers with high power conversion efficiency (PCE) and output power are heavily investigated driven by more energy-efficient commercial applications. In this paper, an asymmetric broad area laser (A-BAL) design is studied and compared with a conventional symmetric broad area laser (S-BAL) design for 808 nm single emitter laser diodes. We present a comparative theoretical and experimental investigation by studying the thermal effects on the laser parameters. The output characteristics and efficiency loss paths for the designs were analyzed. The leakage of carriers was identified as the primary source of the PCE reduction with temperature. Suppressing this leakage by optimization of the A-BAL design, a record continuous-wave PCE of 68% at 25 degrees C and 60.4% at 75 degrees C were achieved for a single emitter laser with 10 W output power. These devices deliver high efficiency at high temperatures with reliable operation achieving 2000 h of an accelerated aging lifetime without failures.